In a recent review of behavioral, medical and dietary approaches for the treatment of obesity, Leon (19767) concluded that the long-term results of currently used treatments are just as discouraging at present as they were earlier. However, it may be that we have effective treatments but what is needed is research examining which treatment is suitable for what type of subject. This line of inquiry is supported by reviewers of research who uniformly assert that subjects receiving the same treatment exhibit great variability in the magnitude of weight loss (Feinstein, 1960; Gormally, et al., 1976; Stunkard & Mahoney, 1976). Unfortunately, the "patient uniformity myth" (Keisler, 1966) has been perpetuated and the question of how patient characteristics influence response to obesity treatment remains largely neglected. Research is needed to discover predictors which identify individuals who would have the highest probability of success in a given type of treatment. The major aim of this proposal is to examine which subjects are likely to succeed in a behavioral obesity treatment. The first objective is to empirically derive predictors of success for behavior modification utilizing discriminant analysis. The few behavior therapy studies, which attempted to correlate outcome with subject variables, used predictors based on a priori assumptions about the relationship between personality and weight loss. In contrast, a discriminant analysis approach yields an empirically based set of predictors derived from the comparison of successful and unsuccessful weight losers. The second objective is to validate these predictors on another sample of subjects. This objective will be accomplished by using discriminant scores to predict successful outcome in treatment and evaluating the proportion of subjects who actually succeed relative to those predicted to succeed.